Motor-driven compressor

ABSTRACT

A motor-driven compressor includes an electric motor, a compression mechanism, which compresses gas by being driven by the electric motor, and a body accommodating the electric motor and the compression mechanism. The motor-driven compressor includes a motor control section, which drives the electric motor by controlling power supply to the electric motor, a vibration control section, which generates a waveform in a phase opposite to the waveform of vibration predicted to be generated in the body due to the driving of the electric motor, and a vibration applying device, which is located on the body and applies vibration in the opposite phase generated by the vibration control section to the body.

BACKGROUND OF THE INVENTION

The present invention relates to a motor-driven compressor that can reduce driving noise.

In a prior-art hybrid vehicle or an electric automobile on which an electric motor is mounted as a drive source for propelling the vehicle, noise due to driving of the electric motor is reduced by putting the electric motor into a non-operating state when the vehicle is temporarily stopped. In vehicles such as hybrid cars, a motor-driven compressor is mounted to make the air conditioner usable regardless of the driving state of the electric motor for propelling.

However, if the motor-driven compressor is mounted on a vehicle such as a hybrid car, noise might become a problem, since the motor-driven compressor is driven while the electric motor for propelling the vehicle is not operating. A silencing device that cancels the driving noise of the compressor has been proposed regarding that problem. See Japanese Laid-Open Patent Publication No. 4-334713.

According to the silencing device of the publication, sound in the phase opposite to that of the driving noise generated from the compressor is output from a speaker to cancel the driving noise of the compressor. Thus, the silencing device can suppress the driving noise of the compressor to the outside.

In the silencing device, the speaker needs to be provided separately from the compressor and in the vicinity of the body of the compressor. On the other hand, in the recent automobiles including hybrid cars, a large number of components need to be mounted in line with sophistication of vehicle control, and as a result, there is a problem that a space for disposing new components cannot be sufficiently ensured. Therefore, the silencing device is difficult to be mounted on a vehicle separately from the compressor.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a motor-driven compressor that can be located in a space-saving manner and can suppress noise.

To achieve the foregoing objective and in accordance with one aspect of the present invention, a motor-driven compressor is provided that includes an electric motor, a compression mechanism, a body, a motor control section, a waveform generation section and at least one vibration applying device. The compression mechanism is driven by the electric motor to compress gas. The body accommodates the electric motor and the compression mechanism. The motor control section drives the electric motor by controlling a power supply to the electric motor. The waveform generation section generates a waveform in a phase opposite to the waveform of vibration predicted to be generated in the body due to driving of the electric motor. The vibration applying device is located on the body and applies to the body vibration having the waveform in the opposite phase generated by the waveform generation section.

Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1A is a schematic side view of a motor-driven compressor;

FIG. 1B is a schematic front view of the motor-driven compressor;

FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1B; and

FIG. 3 is a schematic side view of a motor-driven compressor according to another embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A motor-driven scroll compressor 10 according to one embodiment of the present invention will be described below with reference to FIGS. 1A, 1B, and 2. In the following description, forward are rearward directions are defined as directions of arrow Y1 in FIG. 1A. Upward and downward directions are defined as directions of arrow Y2 in FIG. 1A. Likewise, leftward and rightward directions are defined as directions of arrow Y3 in FIG. 1B.

As illustrated in FIGS. 1A and 1B, mounting portions 13 for fixing the motor-driven compressor 10 to a base 12 are formed on a housing 11 of the motor-driven compressor 10. In this embodiment, the housing 11 and the mounting portions 13 constitute a body KT of the motor-driven compressor 10. The base 12 is an inner wall surface of a drive source chamber, accommodating a motor, which is a drive source for vehicle running, in a hybrid car or an electric automobile, for example. The mounting portions 13 are fixed by fasteners such as bolts while a distal end face 13 a, as a contact portion, is in contact with the base 12.

As illustrated in FIG. 2, the housing 11 includes a cylindrical first housing member 11 a, which extends in the forward-rearward direction and has a closed one end, and a cylindrical second housing member 11 b, which extends in the forward-rearward direction and has a closed one end. The first and second housing members 11 a and 11 b are fixed to each other by fastening tools such as bolts. The first housing member 11 a and the second housing member 11 b are formed by die casting an aluminum alloy.

A suction hole 14 for taking in gas to be compressed by the motor-driven compressor 10, that is, refrigerant gas, is formed in the first housing member 11 a. Moreover, a rotary shaft 15 as an output shaft is located in the first housing member 11 a so as to extend in the forward-rearward direction. The rotary shaft 15 is supported to be rotational around an axis L of the rotary shaft 15 by a bearing 16 and a bearing 17 located respectively at the ends thereof. A permanent-magnet embedded type rotor 20 is fixed on the rotary shaft 15 to be rotational integrally with the rotary shaft 15.

Moreover, teeth 21 a are formed on an inner peripheral surface of the first housing member 11 a to surround the rotor 20. A stator coil 21 b is wound around each of the teeth 21 a. The teeth 21 a and the stator coil 21 b form a stator 21. In this embodiment, an electric motor 23 is formed of the rotary shaft 15, the rotor 20, and the stator 21. The electric motor 23 in this embodiment is a three-phase AC synchronous motor having three coils, that is, a U-phase, a V-phase, and a W-phase as the stator coil 21 b.

The electric motor 23 is accommodated in a motor accommodating chamber 24 of the first housing member 11 a. The bearing 17, which supports the front side of the rotary shaft 15, is located on a partition wall 25, which defines the motor accommodating chamber 24 in the first housing member 11 a. The front end of the rotary shaft 15 is inserted through an insertion hole 25 a formed in the partition wall 25.

An eccentric shaft 15 a is formed at a position eccentrically with respect to the axis L of the rotary shaft 15 on the front end face of the rotary shaft 15. The eccentric shaft 15 a supports a movable scroll member 30 as a movable member through the bearing 27. The movable scroll member 30 includes a disk-shaped base plate 30 a and a movable scroll portion 30 b extending forward from the base plate 30 a. The movable scroll member 30 orbits around the axis L of the rotary shaft 15, that is, makes a revolving motion while a rotating motion around the eccentric shaft 15 a is restricted when the rotary shaft 15 is rotated.

A fixed scroll member 31 is fixed at an opening end of the first housing member 11 a. The fixed scroll member 31 includes a disk-shaped base plate 31 a, a cylindrical outer peripheral wall 31 b extending from the peripheral edge portion of the base plate 31 a, and a fixed scroll portion 31 c extending rearward from the base plate 31 a inside the outer peripheral wall 31 b. A distal end face of the outer peripheral wall 31 b is joined to the front face of the partition wall 25. The base plate 31 a of the fixed scroll member 31, the outer peripheral wall 31 b, and the partition wall 25 define a scroll accommodating chamber 33. A communication hole 25 b, which makes the motor accommodating chamber 24 communicate with the scroll accommodating chamber 33, is formed in the partition wall 25.

The movable scroll member 30 and the fixed scroll member 31 are located so that a movable scroll portion 30 b and a fixed scroll portion 31 c cooperate with each other in the scroll accommodating chamber 33, and also, the respective distal end faces are brought into contact with the base plates 30 a and 31 a of the scroll members 30 and 31 on the other side.

Therefore, the base plate 30 a and the movable scroll portion 30 b of the movable scroll member 30 and the base plate 31 a and the fixed scroll portion 31 c of the fixed scroll member 31 define a compression chamber 34 in the scroll accommodating chamber 33. In this embodiment, the movable scroll member 30 and the fixed scroll member 31 constitute a compression mechanism 32.

A suction chamber 35 for taking in gas into the compression chamber 34 is defined between the outer peripheral wall 31 b of the fixed scroll member 31 and an outermost peripheral portion of the movable scroll portion 30 b of the movable scroll member 30. The suction chamber 35 is connected to the communication hole 25 b through a suction passage 36.

A discharge chamber 37 is defined on the front of the fixed scroll member 31 by joining the second housing member 11 b and the fixed scroll member 31. A discharge hole 31 d, which connects the compression chamber 34 to the discharge chamber 37, is formed at the center of the base plate 31 a in the fixed scroll member 31.

A discharge valve 40 made of a lead valve, which opens/closes the discharge hole 31 d, is located on the surface opposing the discharge chamber 37 of the fixed scroll member 31. The discharge valve 40 prevents a compressed gas discharged from the compression mechanism 32 from flowing back to the compression mechanism 32. Moreover, a retainer 41, which regulates an opening degree of the discharge valve 40, is fixed to the side opposing the discharge chamber 37 of the fixed scroll member 31. The discharge valve 40 operates in the forward-rearward direction between a seal position at which the discharge hole 31 d is sealed by contact with the fixed scroll member 31 and an open position at which the discharge hole 31 d is opened when urged by the compressed gas toward the retainer 41.

Moreover, a discharge hole 42, which discharges compressed gas in the discharge chamber 37, that is, a high-pressure refrigerant gas, is formed in the second housing member 11 b.

When the rotary shaft 15 is driven by power supplied to the electric motor 23, the movable scroll member 30 orbits around the axis of the fixed scroll member 31, that is, an axis L of the rotary shaft 15 through the eccentric shaft 15 a. The compression chamber 34 is moved toward the center from the outer periphery of each of the scroll portions 30 b and 31 c of the both scroll members 30 and 31 while decreasing the volume by the orbiting motion of the movable scroll member 30. As a result, the gas taken into the compression chamber 34 from the suction chamber 35 is compressed. Then, the gas compressed by the compression mechanism 32 is discharged to the discharge chamber 37 from the discharge hole 31 d through the discharge valve 40.

Moreover, gas is taken in through the suction hole 14 of the first housing member 11 a as the compression mechanism 32 operates. The taken-in gas passes through the communication hole 25 b and the suction passage 36 and is led into the suction chamber 35. Moreover, the compressed gas discharged into the discharge chamber 37 is discharged from the discharge hole 42 to the outside of the motor-driven compressor 10.

Moreover, vibration occurs at each part in the motor-driven compressor 10 due to driving of the electric motor 23, and the body KT is vibrated, accordingly. Vibration with a frequency equal to a rotation speed of the electric motor 23 is transmitted from the electric motor 23 to the body KT by the driving of the electric motor 23, for example.

Vibration mainly in the upward-downward direction, which is orthogonal to the axis L, and the leftward-rightward direction having a frequency equal to the rotation speed of the electric motor 23 is transmitted from the compression mechanism 32 to the body KT by the orbiting motion of the movable scroll member 30 around the axis L of the rotary shaft 15. Vibration due to rubbing between the scroll portions 30 b and 31 c of the scroll members 30 and 31 is transmitted from the compression mechanism 32 to the body KT. Rubbing noise is generated by this vibration. Above the compression mechanism 32 on the outer surface of the body KT is a position most separated from the distal end faces 13 a of the mounting portions 13 and where the vibration becomes the greatest.

Vibration having a frequency equal to the rotation speed of the electric motor 23 is transmitted from the discharge valve 40 to the body KT mainly to the forward-rearward direction as the compressed gas is discharged from the discharge valve 40.

Then, as illustrated in FIGS. 1A and 1B, a front piezoelectric device 45 a, a mounting portion piezoelectric device 45 b, and an upper piezoelectric device 45 c are located on the outer surface of the body KT such as the housing 11 and the mounting portions 13 of the motor-driven compressor 10 as a vibration applying device which applies vibration to the housing 11. Each of the piezoelectric devices 45 a to 45 c is a laminated piezoelectric actuator in which a plurality of piezoelectric devices are laminated and applies vibration to the housing 11 by expansion/contraction according to the applied voltage.

In more detail, the front piezoelectric device 45 a is located on the outer surface of the housing 11 at a portion where the discharge chamber 37 is formed. Moreover, the front piezoelectric device 45 a is located to align with the discharge hole 31 d and the discharge valve 40 in the forward-rearward direction, that is, to face the discharge hole 31 d and the discharge valve 40 when viewed from the front. The front piezoelectric device 45 a applies vibration in the forward-rearward direction to the body KT by application of a voltage.

Moreover, the mounting portion piezoelectric device 45 b is located on the outer surface of the mounting portion 13 on the left side of the motor-driven compressor 10. The mounting portion piezoelectric device 45 b applies vibration in the leftward-rightward direction to the body KT by application of a voltage.

The upper piezoelectric device 45 c is located on the outer surface of the housing 11 at a location of the compression mechanism 32 and an upper side on the outer side in the upward-downward direction, which is orthogonal to the rotary shaft 15 of the electric motor 23. The upper piezoelectric device 45 c is located at a position most separated from the distal end faces 13 a of the mounting portions 13 on the outer surface of the body KT. The upper piezoelectric device 45 c gives vibration in the upward-downward direction to the body KT by application of a voltage.

Subsequently, a motor-driven configuration of the motor-driven compressor 10 will be described in accordance with FIGS. 1A and 1B.

As illustrated in FIGS. 1A and 1B, the motor-driven compressor 10 has a controller 50, which controls operation of the motor-driven compressor 10 mounted thereon. The controller 50 includes a motor control section 51, which drives the electric motor 23 by controlling power supply to the electric motor 23, and a vibration control section 52, which controls an expansion/contraction operation by applying a voltage to each of the piezoelectric devices 45 a to 45 c.

The electric motor 23 and the vibration control section 52 are connected to the motor control section 51. The motor control section 51 includes an inverter circuit composed of a switching element such as IGBT (Insulated Gate Bipolar Transistor). The motor control section 51 converts the power supplied from a DC power supply to a three-phase AC and supplies the power to the electric motor 23 by turning on/off each of the switching elements by means of vector control according to a speed instruction from the outside. In more detail, the motor control section 51 estimates a rotation speed and a rotor position of the rotor 20 of the electric motor 23 by calculation on the basis of an output current from the inverter current or a voltage of the inverter circuit. Then, the motor control section 51 generates a driving waveform signal such as PWM (Pulse Width Modulation) signal on the basis of the estimated rotor position and rotation speed and turns on/off each of the switching elements of the inverter circuit by the generated driving waveform signal.

The vibration control section 52 includes a CPU, which executes various calculation processing, a ROM, which stores calculation programs and various maps, and a RAM, which temporarily stores information such as CPU calculation results. The vibration control section 52 calculates and predicts, that is, estimates a waveform of vibration generated in the body KT due to the driving of the electric motor 23 on the basis of a control state of the electric motor 23 by the motor control section 51. The operation of the vibration control section 52 will be described below in detail.

The ROM of the vibration control section 52 stores a rotation speed of the electric motor 23, that is, a rotation number per unit time and a waveform prediction map associated with the waveform of the vibration generated in the body KT. This waveform prediction map is prepared for the location of each of the piezoelectric devices 45 a to 45 c. Each waveform prediction map is set on the basis of an actually measured value of the vibration waveform at the location of each of the piezoelectric devices 45 a to 45 c on the outer surface of the body KT in accordance with the rotation speed of the electric motor 23.

With the waveform prediction map for the front piezoelectric device 45 a, the waveform of the vibration in the forward-rearward direction at the location of the front piezoelectric device 45 a can be specified on the basis of the rotation speed of the electric motor 23. With the waveform prediction map for the mounting portion piezoelectric device 45 b, the waveform of the vibration in the leftward-rightward direction at the location of the mounting portion piezoelectric device 45 b can be specified on the basis of the rotation speed of the electric motor 23. With the waveform prediction map for the upper piezoelectric device 45 c, the waveform of the vibration in the upward-downward direction in the upper piezoelectric device 45 c can be specified on the basis of the rotation speed of the electric motor 23.

The vibration control section 52 refers to the waveform prediction map on the basis of the rotation speed inputted from the motor control section 51 and predicts a vibration waveform of the body KT at the location of each of the piezoelectric devices 45 a to 45 c. Moreover, the vibration control section 52 predicts a vibration phase of the body KT at the location of each of the piezoelectric devices 45 a to 45 c on the basis of the rotor position inputted from the motor control section 51. As described above, the vibration generated by the operations of the electric motor 23, the compression mechanism 32, and the discharge valve 40 is vibration generated in conjunction with the rotation speed of the electric motor 23, and the phase of the vibration can be predicted from an angular position of the rotor 20 of the electric motor 23.

The vibration control section 52 generates a waveform in the opposite phase on the basis of the waveform and phase of the vibration predicted for the location of each of the piezoelectric devices 45 a to 45 c. Then, the vibration control section 52 applies the vibration in the opposite phase to the body KT by applying a voltage to each of the piezoelectric devices 45 a to 45 c on the basis of the generated waveform in the opposite phase. Moreover, the vibration control section 52 controls each of the piezoelectric devices 45 a to 45 c so as to generate vibration having the same amplitude as that of the predicted vibration. Therefore, the vibration control section 52 of this embodiment functions as a waveform generation section.

Subsequently, operation of the motor-driven compressor 10 having the above configuration will be described.

The front piezoelectric device 45 a applies vibration in the phase opposite to the vibration component to the forward-rearward direction and having the same amplitude in the forward-rearward direction in the vibration predicted to be generated in the located portion of the front piezoelectric device 45 a to the body KT. Therefore, the vibration in the forward-rearward direction in the vibration generated in the body KT is cancelled by the front piezoelectric device 45 a.

The mounting portion piezoelectric device 45 b applies vibration in the phase opposite to the vibration component to the leftward-rightward direction and having the same amplitude in the leftward-rightward direction in the vibration predicted to be generated in the location of the mounting portion piezoelectric device 45 b to the body KT, that is, to the mounting portions 13. Therefore, the vibration in the leftward-rightward direction in the vibration generated in the body KT is cancelled by the mounting portion piezoelectric device 45 b.

Similarly, the upper piezoelectric device 45 c applies vibration in the phase opposite to the vibration component to the upward-downward direction and having the same amplitude in the upward-downward direction in the vibration predicted to be generated in the location of the upper piezoelectric device 45 c to the body KT. Therefore, the vibration in the upward-downward direction in the vibration generated in the body KT is cancelled by the upper piezoelectric device 45 c.

Therefore, the following advantages can be achieved in the present embodiment.

(1) The vibration having the waveform in the phase opposite to that of the waveform of the vibration predicted to be generated in the body KT due to the driving of the electric motor 23 is applied to the body KT by each of the piezoelectric devices 45 a to 45 c. As a result, the vibration generated in the body KT by the driving of the electric motor 23 is cancelled. Thus, noise generated in the body KT can be suppressed. Moreover, there is no need to provide a device that suppresses the noise separately from the motor-driven compressor 10, since each of the piezoelectric devices 45 a to 45 c is located on the body KT. Therefore, the motor-driven compressor 10 can be located in a space-saving manner, and the noise of the motor-driven compressor 10 can be suppressed.

(2) The mounting portion piezoelectric device 45 b is located on one of the mounting portions 13. Thus, the vibration generated in the mounting portions 13 can be favorably suppressed. Therefore, spread of the noise due to propagation of the vibration from the mounting portions 13 to the base 12 can be further suppressed.

(3) The front piezoelectric device 45 a is located on the outer surface of the body KT at the location of the discharge chamber 37. Thus, the capacity of the discharge chamber 37 is not reduced as compared with the disposition of the front piezoelectric device 45 a in the discharge chamber 37. Moreover, the vibration generated when the compressed gas is discharged into the discharge chamber 37 can be suppressed more favorably. Therefore, generation of noise can be further suppressed.

(4) The front piezoelectric device 45 a is located on the outer surface of the body KT so as to face the discharge valve 40 in the operating direction of the discharge valve 40, that is, in the forward-rearward direction. Thus, the vibration generated due to the operation of the discharge valve 40 can be suppressed more favorably. Therefore, generation of the noise can be further suppressed.

(5) The upper piezoelectric device 45 c is located on the outer surface of the body KT at the location of the compression mechanism 32 and on the outside in the direction orthogonal to the axis L of the rotary shaft 15 of the electric motor 23. Thus, the vibration generated when the movable scroll member 30 constituting the compression mechanism 32 orbits, that is, orbits around the axis L of the rotary shaft 15, can be suppressed more favorably. Therefore, generation of the noise can be further suppressed.

(6) Moreover, the upper piezoelectric device 45 c is located at a position most separated from the distal end faces 13 a in the mounting portions 13. Thus, it is possible to more favorably suppress vibration of the body KT, which increases as the distance from the distal end faces 13 a of the mounting portions 13 fixed to the base 12 increases. Therefore, generation of the noise can be further suppressed.

(7) The vibration in the phase opposite to the vibration predicted at the respective locations is applied to the body KT by each of the piezoelectric devices 45 a to 45 c. Therefore, the vibration can be cancelled more effectively than the application of the vibration having common waveform by the piezoelectric devices 45 a to 45 c to the body KT.

(8) The vibration in the forward-rearward direction, the leftward-rightward direction, and the upward-downward direction is applied by each of the piezoelectric devices 45 a to 45 c. Therefore, the vibration in all the directions generated in the body KT can be cancelled. Therefore, generation of the noise can be further suppressed.

(9) The vibration control section 52 predicts the waveform of the vibration generated in the body KT on the basis of the rotation speed and the rotor position of the electric motor 23, and generates a waveform in the opposite phase. Therefore, even if the operation state of the electric motor 23, that is, the rotation speed or the rotor position is continuously changing, the waveform of the vibration generated in the body KT can be continuously predicted, and the vibration in the phase opposite to the predicted vibration can be applied to the body KT. Therefore, generation of the noise can be favorably suppressed.

It should be understood that the invention may be embodied in the following forms without departing from the spirit or scope of the invention.

The vibration control section 52 may be configured to be capable of executing feedback control on the basis of the vibration waveform of the body KT detected by a vibration sensor located on the body KT of the motor-driven compressor 10. As illustrated in FIG. 3, for example, vibration sensors 60 a to 60 c, each formed of a piezoelectric device, are placed at locations of the piezoelectric devices 45 a to 45 c, respectively, and connected to the vibration control section 52. Then, the vibration control section 52 corrects a waveform in the opposite phase so that the amplitude of the vibration detected by each of the vibration sensors 60 a to 60 c becomes smaller, on the basis of the vibration waveform of the body KT detected by the vibration sensors 60 a to 60 c. In this case, the vibration control section 52 functions as a waveform correction section. According to this configuration, the waveform in the opposite phase generated by the vibration control section 52 is corrected so that the vibration detected by each of the vibration sensors 60 a to 60 c, that is, the amplitude becomes smaller. Thus, in addition to the application of the vibration of the waveform in the phase opposite to the waveform of the predicted vibration, the vibration generated in the body KT can be further suppressed by correcting the waveform in the opposite phase. If a sensor that can detect vibration in the forward-rearward direction, the leftward-rightward direction, and the upward-downward direction is used as a vibration sensor, one sensor can be used instead of the vibration sensors 60 a to 60 c.

Other actuators including a piston and an electric motor may be used as a vibration applying device.

One or two piezoelectric devices in the piezoelectric devices 45 a to 45 c may be omitted. Alternatively, four or more piezoelectric devices may be employed. That is, the number of the vibration applying devices may be changed as appropriate.

The piezoelectric devices 45 a to 45 c may be located inside the body KT. The piezoelectric devices 45 a to 45 c may be located on the partition wall 25 or on the inner face of the second housing member lib forming the discharge chamber 37, for example. Moreover, the piezoelectric device may be located on the distal end faces 13 a of the mounting portions 13 and the vibration applying device may be located between the distal end face 13 a and the base 12. By configuring as above, the vibration in the upward-downward direction may be applied to the body KT, and propagation of the vibration from the body KT to the base 12 can be suppressed. As described above, the location of the vibration application portion may be changed as appropriate.

In the motor-driven compressor 10, a rotation speed sensor that detects a rotation speed of the electric motor 23 may be employed, and the motor control section 51 may control supply power to the electric motor 23 on the basis of the rotation speed detected by the rotation speed sensor. In this case, the vibration control section 52 may calculate and predict the waveform of vibration generated in the body KT on the basis of the rotation speed detected by the rotation speed sensor.

The vibration control section 52 may predict the waveform of vibration generated in the body KT on the basis of a temperature of a region accommodating the controller 50 such as inverter circuit or a torque occurring in the electric motor 23, and generate a waveform in the opposite phase. In this case, a waveform prediction map that associates the temperature with the waveform of vibration or a waveform prediction map that associates the torque with the waveform of vibration may be used.

The vibration control section 52 may predict the waveform of vibration generated in the body KT by calculation without using the waveform prediction map.

The motor control section 51 and the vibration control section 52 may be provided in a separate controller. The controller 50 may also work as other controllers.

The present invention may be embodied in a motor-driven compressor with a different mechanism such as a diaphragm compressor using the electric motor 23 as a driving source, a rotary compressor, a swash plate compressor and the like.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims. 

1. A motor-driven compressor comprising: an electric motor; a compression mechanism, which is driven by the electric motor to compress gas; a body, which accommodates the electric motor and the compression mechanism; a motor control section, which drives the electric motor by controlling a power supply to the electric motor; a waveform generation section, which generates a waveform in a phase opposite to the waveform of vibration predicted to be generated in the body due to driving of the electric motor; and at least one vibration applying device, which is located on the body and applies to the body vibration having the waveform in the opposite phase generated by the waveform generation section.
 2. The motor-driven compressor according to claim 1, further comprising: a vibration detection section, which detects vibration generated in the body due to driving of the electric motor; and a waveform correction section, which, on the basis of a detection result of the vibration detection section, corrects the waveform in the opposite phase generated by the waveform generation section such that the vibration detected by the vibration detection section decreases.
 3. The motor-driven compressor according to claim 1, wherein the body includes a mounting portion, which fixes the body to a base, and the at least one vibration applying device is located on the mounting portion.
 4. The motor-driven compressor according to claim 1, wherein the body has an outer surface and a discharge chamber into which compressed gas is discharged from the compression mechanism therein; and the at least one vibration applying device is located on the outer surface of the body at a portion where the discharge chamber is formed.
 5. The motor-driven compressor according to claim 4, further comprising: a discharge valve, which is provided in the discharge chamber and prevents the compressed gas discharged from the compression mechanism from flowing back to the compression mechanism, wherein the at least one vibration applying device is located to face the discharge valve.
 6. The motor-driven compressor according to claim 1, wherein the electric motor includes an output shaft, the body has an outer surface, the compression mechanism includes a movable member, which is fixed to the output shaft of the electric motor and orbits around an axis of the output shaft along with driving of the electric motor, and the at least one vibration applying device is oriented in a direction orthogonal to the output shaft of the electric motor and located on the outer surface of the body at a portion where the compression mechanism is located.
 7. The motor-driven compressor according to claim 6 wherein the electric motor includes a rotor fixed to the output shaft, and the waveform generation section predicts a phase of vibration generated in the body from an angular position of the rotor.
 8. The motor-driven compressor according to claim 1, wherein the body includes a mounting portion, which fixes the body to a base, and the body has an outer surface, and the at least one vibration applying device is located on the outer surface of the body and at a position most separated from a contact portion of the base in the mounting portion.
 9. The motor-driven compressor according to claim 1, wherein the waveform generation section predicts a waveform of vibration generated in the body on the basis of a rotation speed of the electric motor.
 10. The motor-driven compressor according to claim 1, wherein the at least one vibration applying device includes a piezoelectric device, which applies vibration to the body through expansion/contraction according to an applied voltage. 